Add rework pricing type (Fixed vs Per-Item) and inline rework flow on Job Details

Adds a PricingType enum to ReworkRecord (FixedPrice | PerItem), surfaces the
choice in the rework modal on Job Details, and wires the resulting unit/total
price display. Includes migration AddReworkPricingType, updated repository
query for rework history, and help article updates.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/PowderCoating.Core/Entities/ReworkRecord.cs

@@ -31,6 +31,9 @@ public class ReworkRecord : BaseEntity
     public bool IsBillableToCustomer { get; set; }
     public string? BillingNotes { get; set; }
 
+    // Pricing attribution for the linked rework job (null on pre-existing records)
+    public ReworkPricingType? ReworkPricingType { get; set; }
+
     // ── Resolution ────────────────────────────────────────────────────────────
     public ReworkStatus Status { get; set; } = ReworkStatus.Open;
     public ReworkResolution? Resolution { get; set; }